/****************************************************************//**
 *
 * @file tftp_server.c
 *
 * @author   Logan Gunthorpe <logang@deltatee.com>
 *           Dirk Ziegelmeier <dziegel@gmx.de>
 *
 * @brief    Trivial File Transfer Protocol (RFC 1350)
 *
 * Copyright (c) Deltatee Enterprises Ltd. 2013
 * All rights reserved.
 *
 ********************************************************************/

/*
 * Redistribution and use in source and binary forms, with or without
 * modification,are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright notice,
 *    this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright notice,
 *    this list of conditions and the following disclaimer in the documentation
 *    and/or other materials provided with the distribution.
 * 3. The name of the author may not be used to endorse or promote products
 *    derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO
 * EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
 * TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 * Author: Logan Gunthorpe <logang@deltatee.com>
 *         Dirk Ziegelmeier <dziegel@gmx.de>
 *
 */

/**
 * @defgroup tftp TFTP server
 * @ingroup apps
 *
 * This is simple TFTP server for the lwIP raw API.
 */

#include "lwip/apps/tftp_server.h"

#if LWIP_UDP

#include "lwip/udp.h"
#include "lwip/timeouts.h"
#include "lwip/debug.h"

#define TFTP_MAX_PAYLOAD_SIZE 512
#define TFTP_HEADER_LENGTH    4

#define TFTP_RRQ   1
#define TFTP_WRQ   2
#define TFTP_DATA  3
#define TFTP_ACK   4
#define TFTP_ERROR 5

enum tftp_error {
	TFTP_ERROR_FILE_NOT_FOUND    = 1,
	TFTP_ERROR_ACCESS_VIOLATION  = 2,
	TFTP_ERROR_DISK_FULL         = 3,
	TFTP_ERROR_ILLEGAL_OPERATION = 4,
	TFTP_ERROR_UNKNOWN_TRFR_ID   = 5,
	TFTP_ERROR_FILE_EXISTS       = 6,
	TFTP_ERROR_NO_SUCH_USER      = 7
};

#include <string.h>

struct tftp_state {
	const struct tftp_context* ctx;
	void* handle;
	struct pbuf* last_data;
	struct udp_pcb* upcb;
	ip_addr_t addr;
	u16_t port;
	int timer;
	int last_pkt;
	u16_t blknum;
	u8_t retries;
	u8_t mode_write;
};

static struct tftp_state tftp_state;

static void tftp_tmr(void* arg);

static void
close_handle(void)
{
	tftp_state.port = 0;
	ip_addr_set_any(0, &tftp_state.addr);

	if(tftp_state.last_data != NULL) {
		pbuf_free(tftp_state.last_data);
		tftp_state.last_data = NULL;
	}

	sys_untimeout(tftp_tmr, NULL);

	if(tftp_state.handle) {
		tftp_state.ctx->close(tftp_state.handle);
		tftp_state.handle = NULL;
		LWIP_DEBUGF(TFTP_DEBUG | LWIP_DBG_STATE, ("tftp: closing\n"));
	}
}

static void
send_error(const ip_addr_t* addr, u16_t port, enum tftp_error code, const char* str)
{
	int str_length = strlen(str);
	struct pbuf* p;
	u16_t* payload;

	p = pbuf_alloc(PBUF_TRANSPORT, (u16_t)(TFTP_HEADER_LENGTH + str_length + 1), PBUF_RAM);

	if(p == NULL) {
		return;
	}

	payload = (u16_t*) p->payload;
	payload[0] = PP_HTONS(TFTP_ERROR);
	payload[1] = lwip_htons(code);
	MEMCPY(&payload[2], str, str_length + 1);

	udp_sendto(tftp_state.upcb, p, addr, port);
	pbuf_free(p);
}

static void
send_ack(u16_t blknum)
{
	struct pbuf* p;
	u16_t* payload;

	p = pbuf_alloc(PBUF_TRANSPORT, TFTP_HEADER_LENGTH, PBUF_RAM);

	if(p == NULL) {
		return;
	}

	payload = (u16_t*) p->payload;

	payload[0] = PP_HTONS(TFTP_ACK);
	payload[1] = lwip_htons(blknum);
	udp_sendto(tftp_state.upcb, p, &tftp_state.addr, tftp_state.port);
	pbuf_free(p);
}

static void
resend_data(void)
{
	struct pbuf* p = pbuf_alloc(PBUF_TRANSPORT, tftp_state.last_data->len, PBUF_RAM);

	if(p == NULL) {
		return;
	}

	if(pbuf_copy(p, tftp_state.last_data) != ERR_OK) {
		pbuf_free(p);
		return;
	}

	udp_sendto(tftp_state.upcb, p, &tftp_state.addr, tftp_state.port);
	pbuf_free(p);
}

static void
send_data(void)
{
	u16_t* payload;
	int ret;

	if(tftp_state.last_data != NULL) {
		pbuf_free(tftp_state.last_data);
	}

	tftp_state.last_data = pbuf_alloc(PBUF_TRANSPORT, TFTP_HEADER_LENGTH + TFTP_MAX_PAYLOAD_SIZE, PBUF_RAM);

	if(tftp_state.last_data == NULL) {
		return;
	}

	payload = (u16_t*) tftp_state.last_data->payload;
	payload[0] = PP_HTONS(TFTP_DATA);
	payload[1] = lwip_htons(tftp_state.blknum);

	ret = tftp_state.ctx->read(tftp_state.handle, &payload[2], TFTP_MAX_PAYLOAD_SIZE);

	if(ret < 0) {
		send_error(&tftp_state.addr, tftp_state.port, TFTP_ERROR_ACCESS_VIOLATION, "Error occured while reading the file.");
		close_handle();
		return;
	}

	pbuf_realloc(tftp_state.last_data, (u16_t)(TFTP_HEADER_LENGTH + ret));
	resend_data();
}

static void
recv(void* arg, struct udp_pcb* upcb, struct pbuf* p, const ip_addr_t* addr, u16_t port)
{
	u16_t* sbuf = (u16_t*) p->payload;
	int opcode;

	LWIP_UNUSED_ARG(arg);
	LWIP_UNUSED_ARG(upcb);

	if(((tftp_state.port != 0) && (port != tftp_state.port)) ||
	        (!ip_addr_isany_val(tftp_state.addr) && !ip_addr_cmp(&tftp_state.addr, addr))) {
		send_error(addr, port, TFTP_ERROR_ACCESS_VIOLATION, "Only one connection at a time is supported");
		pbuf_free(p);
		return;
	}

	opcode = sbuf[0];

	tftp_state.last_pkt = tftp_state.timer;
	tftp_state.retries = 0;

	switch(opcode) {
		case PP_HTONS(TFTP_RRQ): /* fall through */
		case PP_HTONS(TFTP_WRQ): {
			const char tftp_null = 0;
			char filename[TFTP_MAX_FILENAME_LEN + 1] = { 0 };
			char mode[TFTP_MAX_MODE_LEN] = { 0 };
			u16_t filename_end_offset;
			u16_t mode_end_offset;

			if(tftp_state.handle != NULL) {
				send_error(addr, port, TFTP_ERROR_ACCESS_VIOLATION, "Only one connection at a time is supported");
				break;
			}

			sys_timeout(TFTP_TIMER_MSECS, tftp_tmr, NULL);

			/* find \0 in pbuf -> end of filename string */
			filename_end_offset = pbuf_memfind(p, &tftp_null, sizeof(tftp_null), 2);

			if((u16_t)(filename_end_offset - 2) > sizeof(filename)) {
				send_error(addr, port, TFTP_ERROR_ACCESS_VIOLATION, "Filename too long/not NULL terminated");
				break;
			}

			pbuf_copy_partial(p, filename, filename_end_offset - 2, 2);

			/* find \0 in pbuf -> end of mode string */
			mode_end_offset = pbuf_memfind(p, &tftp_null, sizeof(tftp_null), filename_end_offset + 1);

			if((u16_t)(mode_end_offset - filename_end_offset) > sizeof(mode)) {
				send_error(addr, port, TFTP_ERROR_ACCESS_VIOLATION, "Mode too long/not NULL terminated");
				break;
			}

			pbuf_copy_partial(p, mode, mode_end_offset - filename_end_offset, filename_end_offset + 1);

			tftp_state.handle = tftp_state.ctx->open(filename, mode, opcode == PP_HTONS(TFTP_WRQ));
			tftp_state.blknum = 1;

			if(!tftp_state.handle) {
				send_error(addr, port, TFTP_ERROR_FILE_NOT_FOUND, "Unable to open requested file.");
				break;
			}

			LWIP_DEBUGF(TFTP_DEBUG | LWIP_DBG_STATE, ("tftp: %s request from ", (opcode == PP_HTONS(TFTP_WRQ)) ? "write" : "read"));
			ip_addr_debug_print(TFTP_DEBUG | LWIP_DBG_STATE, addr);
			LWIP_DEBUGF(TFTP_DEBUG | LWIP_DBG_STATE, (" for '%s' mode '%s'\n", filename, mode));

			ip_addr_copy(tftp_state.addr, *addr);
			tftp_state.port = port;

			if(opcode == PP_HTONS(TFTP_WRQ)) {
				tftp_state.mode_write = 1;
				send_ack(0);
			} else {
				tftp_state.mode_write = 0;
				send_data();
			}

			break;
		}

		case PP_HTONS(TFTP_DATA): {
			int ret;
			u16_t blknum;

			if(tftp_state.handle == NULL) {
				send_error(addr, port, TFTP_ERROR_ACCESS_VIOLATION, "No connection");
				break;
			}

			if(tftp_state.mode_write != 1) {
				send_error(addr, port, TFTP_ERROR_ACCESS_VIOLATION, "Not a write connection");
				break;
			}

			blknum = lwip_ntohs(sbuf[1]);
			pbuf_header(p, -TFTP_HEADER_LENGTH);

			ret = tftp_state.ctx->write(tftp_state.handle, p);

			if(ret < 0) {
				send_error(addr, port, TFTP_ERROR_ACCESS_VIOLATION, "error writing file");
				close_handle();
			} else {
				send_ack(blknum);
			}

			if(p->tot_len < TFTP_MAX_PAYLOAD_SIZE) {
				close_handle();
			}

			break;
		}

		case PP_HTONS(TFTP_ACK): {
			u16_t blknum;
			int lastpkt;

			if(tftp_state.handle == NULL) {
				send_error(addr, port, TFTP_ERROR_ACCESS_VIOLATION, "No connection");
				break;
			}

			if(tftp_state.mode_write != 0) {
				send_error(addr, port, TFTP_ERROR_ACCESS_VIOLATION, "Not a read connection");
				break;
			}

			blknum = lwip_ntohs(sbuf[1]);

			if(blknum != tftp_state.blknum) {
				send_error(addr, port, TFTP_ERROR_UNKNOWN_TRFR_ID, "Wrong block number");
				break;
			}

			lastpkt = 0;

			if(tftp_state.last_data != NULL) {
				lastpkt = tftp_state.last_data->tot_len != (TFTP_MAX_PAYLOAD_SIZE + TFTP_HEADER_LENGTH);
			}

			if(!lastpkt) {
				tftp_state.blknum++;
				send_data();
			} else {
				close_handle();
			}

			break;
		}

		default:
			send_error(addr, port, TFTP_ERROR_ILLEGAL_OPERATION, "Unknown operation");
			break;
	}

	pbuf_free(p);
}

static void
tftp_tmr(void* arg)
{
	LWIP_UNUSED_ARG(arg);

	tftp_state.timer++;

	if(tftp_state.handle == NULL) {
		return;
	}

	sys_timeout(TFTP_TIMER_MSECS, tftp_tmr, NULL);

	if((tftp_state.timer - tftp_state.last_pkt) > (TFTP_TIMEOUT_MSECS / TFTP_TIMER_MSECS)) {
		if((tftp_state.last_data != NULL) && (tftp_state.retries < TFTP_MAX_RETRIES)) {
			LWIP_DEBUGF(TFTP_DEBUG | LWIP_DBG_STATE, ("tftp: timeout, retrying\n"));
			resend_data();
			tftp_state.retries++;
		} else {
			LWIP_DEBUGF(TFTP_DEBUG | LWIP_DBG_STATE, ("tftp: timeout\n"));
			close_handle();
		}
	}
}

/** @ingroup tftp
 * Initialize TFTP server.
 * @param ctx TFTP callback struct
 */
err_t
tftp_init(const struct tftp_context* ctx)
{
	err_t ret;

	struct udp_pcb* pcb = udp_new_ip_type(IPADDR_TYPE_ANY);

	if(pcb == NULL) {
		return ERR_MEM;
	}

	ret = udp_bind(pcb, IP_ANY_TYPE, TFTP_PORT);

	if(ret != ERR_OK) {
		udp_remove(pcb);
		return ret;
	}

	tftp_state.handle    = NULL;
	tftp_state.port      = 0;
	tftp_state.ctx       = ctx;
	tftp_state.timer     = 0;
	tftp_state.last_data = NULL;
	tftp_state.upcb      = pcb;

	udp_recv(pcb, recv, NULL);

	return ERR_OK;
}

#endif /* LWIP_UDP */
